fix JetPsiUtil.deleteClass() so that it no longer tries to delete the entire file when deleting a nested class or object

#KT-7483 Fixed

idea/testData/safeDelete/deleteObject/kotlinObject/companionObject.kt

@@ -0,0 +1,6 @@
+
+class A {
+    fun foo(): Int = 0
+
+    companion ob<caret>ject {}
+}

idea/testData/safeDelete/deleteObject/kotlinObject/companionObject.kt.after

@@ -0,0 +1,4 @@
+class A {
+    fun foo(): Int = 0
+
+}

idea/tests/org/jetbrains/kotlin/safeDelete/JetSafeDeleteTestGenerated.java

@@ -133,6 +133,12 @@ public class JetSafeDeleteTestGenerated extends AbstractJetSafeDeleteTest {
             doObjectTest(fileName);
         }
 
+        @TestMetadata("companionObject.kt")
+        public void testCompanionObject() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/testData/safeDelete/deleteObject/kotlinObject/companionObject.kt");
+            doObjectTest(fileName);
+        }
+
         @TestMetadata("localObject1.kt")
         public void testLocalObject1() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("idea/testData/safeDelete/deleteObject/kotlinObject/localObject1.kt");